This program is designed to explore the effect of delta 9- tetrahydrocannabinol (delta 9-THC) on growth and differentiation in vertebrate systems. The short, well-defined period of metamorphosis which characterizes the transformation of the larval tadpole to adult frog provides an ideal opportunity to use this animal as the model for testing possible toxic and/or teratological effects of a drug on a variety of developmental processes, including growth of new structures, the normal regression of larval structures not needed by the adult, and remodeling of other structures which will remain in the adult but which will have an altered function from those of the larvae. In addition to assessing possible anatomical and physiological effects of delta 9 THC on developmental processes, the tissues involved in the metabolic breakdown of the drug and its accumulation will be studied at various periods of development.